Apparatus for measuring errors of aiming and firing in practice firing against moving targets



June 20, 1 939. F. E. FISCHER 2,162,767 APPARATUS FOR MEASURING ERRORSOF AIMING AND FIRING IN PRACTICE FIRING AGAINST MOVING TARGETS FiledNov. 7, 1956 Patent F 20,

swims t or x :l 1' G EN PRACTICE i 111 scams'r movmc TARGETS raw-1cmErnst Fischer, Erlenbach, Switzerland,

to the firm Contravea A.'-G. Zurich iipplicatlonNovember 7, 1936, SerialNo. 109,802

In All 0:1".

11 Gla In gunnery practice against moving targets, i

especially aircraft, we have to distinguish fundamentally between twodiflerent methods of procedure, i. e. gunnery against towed targets withthe aid of live ammunition on the one hand and gunnery with the aid ofblankammunition together with a simultaneous survey of theairplane-trajectory on the other hand The shooting against towed targetshas the disadvantage that these towed targets are by far less mobile ormovable than the airplane itself. Gunnery practice with blind or blankammunition up to now has followed more or less the following lines: Theairplane-trajectory is surveyed and recorded both as to position andtime in a continuous way and manner by means of cinematographicphoto-theodolites, and the time, the timing of the projectiles, side andelevation of the guns are recorded at the moment of discharging the gun;with the aid of said records it then is possible to determine thesighting error. Y Since the speed of an airplane is of the order ofmagnitude of that of the projectile, we must determine beforehand afuture station of the airplane (point of aim) on the basis-as is wellknown-of various hypotheses. The point of aim is a surmised futurestation of the airplane, in which connection the word future is ofcritical importance. After the span of time (mean time of flight of theprojectile), for which the station of the airplane has been assumedbeforehand, has elapsed, the airplane should be stationedat the assumedpoint (be-point). only comes true when and if the hypothesis was basedon the real factors and conditions. The anti-aircraft guns, at themoment of theirdischarge, are sighted toward the point of aim; they,however, shoot at the be-point, since the shell arrives at its point ofdestination (be-point) only after the time of flight of the projectilehas elapsed. The sighting elements of the guns thus have been chosen soas to bring the mean point of hit-with all due forecast-into coincidencewith the be-point. A point of aim then, after a certain length of timehas elapsed (the so-called timing period), turns into the be-point. Thegeometrical distance between the be-point and the true airplane-station(is-point) is called the sighting error. v

The true airplane-station is found by means of This, however,

film pictures which have been taken-figures from the moment of the gun'sdischarge-after the timing period has elapsed. The co-ordinates of thebe-point are computed on the basis of the shooting tables, giving us thedata of side, elevation and timing. The sighting error then is found byway of a geometrical formation of differences. We thus will have tofigure the absolute co-ordinates of both of be-point and is-point. Thismethod of procedure is complicated and tiresome and thus consumes muchtime.

The procedure according to the present invention allows us to directlydetermine the sighting error or, as the case may be, the gunnery errorin an essentially more simple way and manner in cases where thephoto-thegdolites or the cinematographic photo-theodolites arecontrolled and steered by and from the guns, timing machines,

commander apparatus and the like by means of motors. According to themethod of procedure along the lines of the present invention, thetranslation of the movements onto the phototheodolites is effected byway of co-ordinate changers and translatory systems with an increasedfixed or changing time of run, i. e. socalled delayers.

In this way the photo-theodolites are continuously directed to thebe-point, and the sighting error can be ascertained from the distancesof the airplane photos from the middle point of the picture upon tworelated photographs.

The apparatus for photogrammetrically meas- "uring sighting and gunneryerrors according to the present invention includes at least twotheodolites of known construction which are electrically connected withthe gun and the charging machine and are directed by the latter byremote control. The actuation of the shutter mechanisms of thephototheodolites likewise proceeds from the gun by remote control, forexample, by the firing signal. An important part of the apparatus of thepresent invention is formed by special delay-producing devices which areconnected in the electrical conductors between the gun and thephototheodoiites and which increase the time for transmitting the valuesfrom the gun to the photo-theodolites by a flight interval correspondingto the ignition timing in any particular case.

A satisfactory form of construction for the delaying devices is oneembodying a moving steel tape. This delaying device includes at leastone moving endless steel tape uponwhich, by means of a so-called speakerhead, magnetic registrations are produced which are received by means itii speaker head to the hearer head. For characterizing a movement, it isnecessary to em ploy series of signs .in several transmission charmels.In

general, a-steel tape delayer must be included in every transmissionchannel for increasing the time interval required for the transmission,which otherwise would be practically instantaneous. This can, however,be eliminated, it according to the present invention theregistrations ofthe series or signs of the different channels are spatially separatedfrom each other upon the steel tape or are accomplished by means ofseveral superposed carrier currents which are modulated by the sendermovements to be transmitted. The changing of the degree of increase ofthe time interval for transmitting the sender movements is accomplishedby changing in known manner the length of steel tape between the speakerhead and the heater head, which can be accomplishd by shifting one' ofthe heads relatively to the other or by keeping the heads stationary andvarying the length of the path of travel of the tape therebetween. V

A satisfactory construction of the apparatus mentioned above isillustrated-by way of exampie-schematically in the accompanying drawing.

The apparatuses 3 and 4 house the delayers with the steel tapes forrecording the registrations of the sender movements for the purpose ofan artificial amplifying of the time of run of the transmission ofmovements and signals onto the phototheodolites l and 2. the changers ofco-ordinates which-in a manner well known-change the artilleristicalco-ordinates with which the guns 6 (in the drawing but one of the latteris shown) are sighted toward the point of aim I into the sightingco-ordinates for the photo-theodolites I and 2. For the purpose oftransmitting movements pertaining to the artilleristical co-ordinates(side-S, elevationE and timing-T) from the guns i onto thephototheodolites land 2 as well as for transmitting the signal A'ofdischarge, electrical circuits l-2l are provided. The transmittance,however, also could take place in a wireless, optical, acoustical ormechanical way and manner.

The data of the co-o'rdinates side B, elevation I and timing T as wellas the signal A of discharge or firing are conveyed onto the maindelayer 3 by way of the lines I, 9 and ll--l3; Said data are delayed inthe .said main delayer by the amount of the time of flight of theproiectile corresponding to'the timing T. After the time delay haselapsed, the values of'side S, eleva- The apparatus 5 contains "mayrender the photogrammetrical evaluation or mapping of the photographicpictures simple. They are transmitted to the photo-theodolites l and 2by way of the lines II, I! and 2' and 2|, respectively.

i The firing signal A, which in the main delayer 3 has been delayed bythe amount of the time of flight of the projectile, is transmitted tothe photo-theodolites l and I by way of the line I! and acts on theirshutter mechanisms. A predelayer' A is connected to the line 8, 9, whichlatter transmits the value of timing T, between the gun or appurtenanttiming machine and the main delayer 3. Said pre-delayer takes thesocalled charging delay into account by pre-delaying the transmittanceoi the timing index by the amount of the charging delay. The latterisset down as that length of time which elapses between the setting of thetiming on the projectile and the moment of firing, and it depends uponthe performance of the operating crew.

The timing value T, thus pre-delayed, together with the data as toelevation and side of the guns at the moment of firing constitute thecollective .values. of the artilleristical'co-ordinates of the point ofaim.

The timing value T not only is transmitted by way of the line I. to themain delayer 3for the purpose of a further delayed transmittance-but atthe same time is made use of, in known manner, for regulating the delayapparatus, since the latter, automatically or in combination with a timeindicator, is controlled corresponding to the timing (time of flight ofthe projectile) Amplifiers may be hooked up-in known mannerto all linesof. transmittance. The apparatuses 3, 4 and 5, however, also may beinterconnected in a diife'rent way from the one shown, in

particular in such -a way that the delay arises between or after thetransformations of the co-ordinates.

The center of thepicture or a special mark on the film corresponds-inthe photo-theodolites pointed by way of the delaying devices in accordwith the sighting of the guns-to the be-point (theoretical, mean pointof detonation).

The field of view of the photo-theodolites may be so chosenby way andmeans of a suitable photographical optical systemthat the airplane to beshot at is represented on the pictures with the greatest degree ofprobability. The linear distance then between the picture of theairplane and the center of the picture is a direct measure for thesighting error in question. In order to be able to ascertain thiserrorthen, a single twinexposure, for example, is sufiicient instead of thefilm exposures of the whole trajectory of the airplane by means of twotheodolites as used heretofore. N0 extensive analytical transformationsare necessary any longer, since the center of the picture corresponds tothe be-point.

Gunnery practice with live ammunition also be surveyedphotogrammetrically-e. g. against manned or unmanned fully movableairplanesin the following manner set forth by way of an example:

The airplane is continuously sighted at and its position registered orsurveyed by means of a sighting or. observation apparatus. Theascertained co-ordinates of sight are transformed in a commanding orcorresponding apparatus into artilleristical ones, andthis is done forthat bepoint at which the airplane is expected to arrive, after the timeof fiight of the projectile has elapsed, according to the method ofextrapolation jectile, so that the photo-theodolites are directed v onwhich the commanding apparatus is based. The guns now, however, are notsighted toward this computed point, but instead toward the appurtenantreflected .image of the latter, e. g. with relation to the verticalplane passing through the connecting line of the two exposureapparatuses (base line) or with relation to any vertical line in space,suitably one through the center of the base line. It now we point two offour exposure apparatuses-which are set up in pairs and which may berepresented e.g.by cinematographic theodoiites-toward the true point andtwo to'- ward the said mirrored point, computed in advance, and if now,furthermore, we release the shutters of the four apparatuses at the samemoment, the gunning and sightingerrors may be found from the appurtenantexposures in question'and thus also the performance factor ofextrapolation of the commanding apparatus ac-, cording to thegeometrical art of photogrammetry.

\ The use of live or ordnance ammunition will not be fatal to the crewof a manned airplane because the manned airplane is only used to beaimed at, the anti-aircraft artillery being enabled thereby to beoperated in correspondence with the mobility of a war-like airplane; theguns however are not sighted toward this manned plane or toward thepoint extrapolated by the fire-director, but toward a point which is ina definite and wellknown geometrical relationship to the former point,e. g. toward a point which is always the geometrically reflected imageof the former point with relation to the vertical plane passing throughthe connecting line of the two exposure apparatuses.

What I claim and desire to secure by Letters Patent is:

1. Apparatus for photogrammetfically measuring sighting and gunneryerrors in gun practice against moving targets, such as aircraft,comprising at least two photo-theodoiites provided with shuttermechanisms, means for electrically connecting said photo-theodoliteswith the gun and its ignition timing machine, mechanism controlled byimpulses transmitted by said connecting means and corresponding to thegun coordinates for directing said photo-theodolites in accordance withthe adjustments of the gun and ignition timing machine, mechanismconnected in said conductors for transforming the transmitted guncoordinates into appropriate phototheodolite values, means controlledfrom the gun upon the same point of aim as the gun, but always after theinstant of the discharge of the projectile by a time intervalcorresponding to the time of 4 flight of the projectile.

2. Apparatus according to claim 1 wherein the delaying device in theelectrical conductors between tlie gun and the photo-theodolitesincludes at least one moving endless steel tape adapted to receivemagnetic registrations for conveying them to a remote point, andincluding further for each steel tape a speaker head for producing theregistrations and a hearer head for receiving the same.

3. Apparatus according to claim 1, wherein the delayer device forincreasing the time required for transmitting a forward and rearwardsender movement is composed of a single moving endless steel tape, aplurality of speaker heads arranged to register at spaced points uponthe steel tape the multiplicity oi. magnetic registrations required forcharacterizing a torward and rearward move ment, and a plurality ofhearer heads for receiving the registrations.

4. Apparatus according to claim 1, wherein the delayer device forincreasing the time for transmission of aforward and rearward sendermovement is composed 01. a single moving endless steel tape, a speakerhead associated with the tape and adapted to produce the multiplicity ofregistrations required for characterizing the forward movements by meansof at least two carrier currents modulated by the sender movement, and ahearer head for receiving the registrations.

5. Apparatus according to claim 1 wherein the delaying device in'theelectrical conductors between the gun and the photo-theodolites includesat least one moving endless steel tape adapted to receive magneticregistrations for conveying them to a remote point, and includingfurther for each steel tape a speaker head for producing theregistrations and a hearer head for receiving the same, and means forvarying the increase of the time interval for transmitting a signal fromthe gun to the photo-theodolites, said means acting to shift the hearerhead in the delayer device along the length of the steel tape relativeto the speaker head.

6. Apparatus according to claim i-wherein the delaying device in theelectrical conductors between the gun and the photo-theodolites includesat least one moving endless steel tape adapted to receive magneticregistrations for conveying them to a remote point, said apparatusincluding further for each steel tape a speaker head for producing theregistrations and a hearer head for receiving the same, and means forvarying the increase of the time interval for transmitting a signal fromthe gun to the photo-theodolites, said means acting to shift the speakerhead in the delayer device along the length of the steel tape relativeto the hearer head.

7. Apparatus according to claim 1, wherein the delaying device in theelectrical conductors between the gun and the photo-theodolites includesat least one moving endless steel tape adapted to receive magneticregistrations for conveying them to a remote point, said apparatusincluding further for each steel tape a speaker head for producing theregistrations and a hearer head for receiving the same, and means forvarying the length of the steel tape between the speaker and hearerheads in the delayer device, whereby the degree of increaseoi the timeof transmission of a signal from the gun to the photo-theodolites isregulated.

8. Apparatus according to claim 1, including a plurality of delayerdevices arranged in series in the electrical conductors for transmittingthe values of the gun to the photo-theodolites, and means for varyingthe degree of time increase of said delayer devices independently ofeach other.

9. Apparatus according to claim 1 for photogrammetrically measuringsighting and gunnery errors in sharp gun practice upon displacedtargets, including at .least four photo-theodolites arranged in pairsofwhich one does not intersect the target at the time of firing butdelayed by the time of flight of the projectile, and a mechanical drivefor so coupling the'photo-theodolites with till each other in pairs,that the second theodolite is directed upon a displaced point of aimwhen the first intersects the true target.

' tinuous obtainment or associated artilleristic co- 10. Apparatusaccording to claim 1 for photogrammetrically measuring sighting andgunnery errors in sharp firing practice upon displaced targets,includingat least tour photo-theodolites arranged in pairs of which oneintersects the target not at the time of firing but after an intervalcorresponding to the time of flight of the projectile, and a devicehaving interchangeable connections for electrically coupling thephoto-theodolites with each other in pairs in such manner that thesecond photo-theodolites of each pair is directed to a displaced pointoi aim when the first intersects the true point of aim.

11. Apparatus according to claim 1 for the conordinate's oi the point ofaim, including a delayer device located in the electrical conductors fortransmitting the ignition timing value, said delayer device comprisingat least one moving endless steel tape, a speaker head associated witheach tape for producing magnetic registrations thereon and a heater headfor each tape for receiving said registrations, said delayer deviceincreasing, by the charging period, the .time of transmission of theignition timing value from the ignition timing machine and one of theaforementioned devices to which the correlated ad- Justments oi the sideand elevation at the gun are directly-transferred.

FRIEDRICH ERNST FISCHER:

